One Japanese soldier has been killed and at least 11 other people were injured, some critically, after a volcanic eruption triggered an avalanche which struck skiers at a mountain resort in Japan on Tuesday.

Japanese media reported many of those injured were apparently hit by volcanic rocks raining down on the ski resort. Two were critically injured and three seriously, national broadcaster NHK said.

Six of those trapped were members of Japan's Ground Self Defense Force (SDF), who were engaged in a winter training maneuver, Defense Minister Itsunori Onodera said. Eventually, all of those submerged by the avalanche were rescued but most were injured and one later died.

Photo taken from a Kyodo News helicopter on January 23, 2018, shows the area surrounding Mt. Kusatsushirane in Gunma Prefecture, northwest of Tokyo, which erupted on the same day.Reuters

Kusatsu-Shirane, a 7,090-foot volcano, erupted on Tuesday morning, the Japanese Meteorological Agency (JMA) said. The agency warned that further eruptions could not be ruled out and that rocks could be blasted as far as one mile from the peak.

Video footage from the top of the resort's gondola showed skiers gliding down the slopes as black rocks plummeted from the skies and snow billowed up as they struck the ground, sometimes just missing skiers. A cloud of black smoke later drifted in.

"There was this huge boom, and a big plume of totally black smoke rose up," one skier told NHK. "I had absolutely no idea what had happened."

A photograph taken at the site and shown on NHK depicted a gondola with a shattered window. At least several of the injuries were due to broken glass.

"Other people appeared to be hurt by the stones, which appeared to be around 10 to 20 cm in size," another skier told NHK.

The resort temporarily lost power, leaving many skiers suspended in gondolas for around half an hour. Around 80 skiers at a hut at the top of the mountain were awaiting rescue, which began by helicopter on Tuesday afternoon.

It was unclear whether the avalanche was caused by the volcanic activity, but they occurred nearly simultaneously.

The warning level for the peak was raised to 3, meaning that people should not climb the mountain, the JMA said.

Japan has 110 active volcanoes and monitors 47 of them around the clock.

According to BBC, Japan's volcanos are of the most seismically active in the world. In 2014, the eruption of Mount Ontake killed 63 people, in what was believed to be the worst volcanic disaster for Japan in almost 90 years.